An Oscillating Water Column (OWC) is a marine renewable energy device, designed to extract power from ocean waters. Generally, the OWC includes a chamber open to the surface of the sea and a turbine. The turbine is required to convert the bi-directional air flow produced by the rising and falling sea surface within the chamber into unidirectional rotary motion of a shaft of the turbine, which is then used to power a generator to generate electricity. Impulse type turbines with fixed guide vanes have been developed. However, the fixed guide vanes do not permit isolation of the turbine rotor from the incoming pneumatic power. As a result, the turbine cannot be stopped during period of excessive input power, for example, during storms. Also, carrying out planned shutdown operations, such as maintenance activities, is difficult.
What is needed then is an OWC that permits controlled shut down of the turbine.